The present invention relates to a copper alloy of high strength and electrical conductivity that is suitable for use in terminals in wiring harnesses installed in electrical automotive parts. The present invention also relates to a process for producing such a copper alloy.
The car industry has been playing an important role as one of the key industries in Japan. With the increase in the number of cars produced and, in particular, with the recent advances in car electronics technology, the use of rerolled copper materials has increased more than before. Wiring harnesses as an important class of automotive electrical parts are not an exception and their use has increased to such an extent that installing as much as 20 kg of wire harnesses 1 km long is one automobile is quite common practice. On the other hand, requirements of modern cars for lighter weight, higher reliability and lower cost have become stringest year by year and this has called for similar demands for wiring harnesses that are lighter in weight and ensure higher reliability and which yet can be manufactured at lower cost. A wiring harness is a unitary assembly of an electrical wire and associated terminals and in order to produce a wiring harness that is lightweight and which features high-density wiring, improvements in the characteristics and reliability of a terminal material are essential.
As mentioned above, terminals materials to be used in wiring harnesses are required to satisfy strict standards for characteristics; stated more specifically, they are required to have a strength of at least 55 kgf/mm.sup.2, a threshold value of spring of at least 40 kgf/mm.sup.2 and an electrical conductivity of at least 45% IACS while exhibiting good press formability, reliability in plating, and resistance to environmental factors. In particular, terminals to be used around the engine room are required to have good properties in terms of resistance to environmental factors and reliability in plating and therefore they must have high resistance to stress relaxation, corrosion and stress corrosion cracking in combination with good weatherability of plating deposited on such terminals. However, it has been very difficult for the prior art to attain those terminal materials that possess all of the characteristics described above and which yet can be manufactured at low cost.